With the fast growth of the voice, data and video services demand, the demand for the transmission bandwidth in the access layer is higher and higher. The access technology of “the last kilometer” represented by the xDSL is difficult to satisfy the user demand for the bandwidth; because the EPON, as one of the PON technologies, has the public characteristics, such as, the high bandwidth, the long distance coverage, the flexible networking, the passive intermediate network node, etc., it, applied to the broadband access network, can improve the network bandwidth and performance and reduce the maintenance cost, and is the next generation optical access technology favored by the major operator.
In the processes, such as, performing the ONU register, automatic finding, and distance measurement, etc., the EPON will all need to separate and analyze the MPCP and the data frame; in this way, the uplink framing module can run correctly. The analysis part mainly has two functions: first, to analyze the MPCP control frame, analyze the information of every field and send it to the control module; second, to extract the frame length information of the data frame and OAM frame, and send the frame length information and the frame indication information together with the frame content to the small cache. Therefore, the subordinate large cache extracts the information of the whole frame from the small cache each time according to the frame start information and the frame length information. Therefore, once the frame length information is caused to have mistakes for a certain reason, then it will cause that the big cache is unable to read the information of the whole frame during every reading out, and cause the link service to be unable to jump out from the dead loop, and unable to resume. So, how to correctly analyze the Ethernet frame and extract the frame length information directly influences whether the back-stage module could work normally and steadily. A solution is, while the back-stage cannot receive the normal data all the time, to tell the analysis module to reset the small cache and the later large cache and enable it to work again. Although the method can make it return to normal, the frame dropping will be very severe.